/* ---------------------------------------------------------------------- * Project: CMSIS DSP Library * Title: arm_rfft_f32.c * Description: RFFT & RIFFT Floating point process function * * $Date: 27. January 2017 * $Revision: V.1.5.1 * * Target Processor: Cortex-M cores * -------------------------------------------------------------------- */ /* * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved. * * SPDX-License-Identifier: Apache-2.0 * * Licensed under the Apache License, Version 2.0 (the License); you may * not use this file except in compliance with the License. * You may obtain a copy of the License at * * www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an AS IS BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ #include "arm_math.h" /* ---------------------------------------------------------------------- * Internal functions prototypes * -------------------------------------------------------------------- */ extern void arm_radix4_butterfly_f32( float32_t * pSrc, uint16_t fftLen, float32_t * pCoef, uint16_t twidCoefModifier); extern void arm_radix4_butterfly_inverse_f32( float32_t * pSrc, uint16_t fftLen, float32_t * pCoef, uint16_t twidCoefModifier, float32_t onebyfftLen); extern void arm_bitreversal_f32( float32_t * pSrc, uint16_t fftSize, uint16_t bitRevFactor, uint16_t * pBitRevTab); void arm_split_rfft_f32( float32_t * pSrc, uint32_t fftLen, float32_t * pATable, float32_t * pBTable, float32_t * pDst, uint32_t modifier); void arm_split_rifft_f32( float32_t * pSrc, uint32_t fftLen, float32_t * pATable, float32_t * pBTable, float32_t * pDst, uint32_t modifier); /** * @ingroup groupTransforms */ /** * @addtogroup RealFFT * @{ */ /** * @brief Processing function for the floating-point RFFT/RIFFT. * @deprecated Do not use this function. It has been superceded by \ref arm_rfft_fast_f32 and will be removed * in the future. * @param[in] *S points to an instance of the floating-point RFFT/RIFFT structure. * @param[in] *pSrc points to the input buffer. * @param[out] *pDst points to the output buffer. * @return none. */ void arm_rfft_f32( const arm_rfft_instance_f32 * S, float32_t * pSrc, float32_t * pDst) { const arm_cfft_radix4_instance_f32 *S_CFFT = S->pCfft; /* Calculation of Real IFFT of input */ if (S->ifftFlagR == 1U) { /* Real IFFT core process */ arm_split_rifft_f32(pSrc, S->fftLenBy2, S->pTwiddleAReal, S->pTwiddleBReal, pDst, S->twidCoefRModifier); /* Complex radix-4 IFFT process */ arm_radix4_butterfly_inverse_f32(pDst, S_CFFT->fftLen, S_CFFT->pTwiddle, S_CFFT->twidCoefModifier, S_CFFT->onebyfftLen); /* Bit reversal process */ if (S->bitReverseFlagR == 1U) { arm_bitreversal_f32(pDst, S_CFFT->fftLen, S_CFFT->bitRevFactor, S_CFFT->pBitRevTable); } } else { /* Calculation of RFFT of input */ /* Complex radix-4 FFT process */ arm_radix4_butterfly_f32(pSrc, S_CFFT->fftLen, S_CFFT->pTwiddle, S_CFFT->twidCoefModifier); /* Bit reversal process */ if (S->bitReverseFlagR == 1U) { arm_bitreversal_f32(pSrc, S_CFFT->fftLen, S_CFFT->bitRevFactor, S_CFFT->pBitRevTable); } /* Real FFT core process */ arm_split_rfft_f32(pSrc, S->fftLenBy2, S->pTwiddleAReal, S->pTwiddleBReal, pDst, S->twidCoefRModifier); } } /** * @} end of RealFFT group */ /** * @brief Core Real FFT process * @param[in] *pSrc points to the input buffer. * @param[in] fftLen length of FFT. * @param[in] *pATable points to the twiddle Coef A buffer. * @param[in] *pBTable points to the twiddle Coef B buffer. * @param[out] *pDst points to the output buffer. * @param[in] modifier twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table. * @return none. */ void arm_split_rfft_f32( float32_t * pSrc, uint32_t fftLen, float32_t * pATable, float32_t * pBTable, float32_t * pDst, uint32_t modifier) { uint32_t i; /* Loop Counter */ float32_t outR, outI; /* Temporary variables for output */ float32_t *pCoefA, *pCoefB; /* Temporary pointers for twiddle factors */ float32_t CoefA1, CoefA2, CoefB1; /* Temporary variables for twiddle coefficients */ float32_t *pDst1 = &pDst[2], *pDst2 = &pDst[(4U * fftLen) - 1U]; /* temp pointers for output buffer */ float32_t *pSrc1 = &pSrc[2], *pSrc2 = &pSrc[(2U * fftLen) - 1U]; /* temp pointers for input buffer */ /* Init coefficient pointers */ pCoefA = &pATable[modifier * 2U]; pCoefB = &pBTable[modifier * 2U]; i = fftLen - 1U; while (i > 0U) { /* outR = (pSrc[2 * i] * pATable[2 * i] - pSrc[2 * i + 1] * pATable[2 * i + 1] + pSrc[2 * n - 2 * i] * pBTable[2 * i] + pSrc[2 * n - 2 * i + 1] * pBTable[2 * i + 1]); */ /* outI = (pIn[2 * i + 1] * pATable[2 * i] + pIn[2 * i] * pATable[2 * i + 1] + pIn[2 * n - 2 * i] * pBTable[2 * i + 1] - pIn[2 * n - 2 * i + 1] * pBTable[2 * i]); */ /* read pATable[2 * i] */ CoefA1 = *pCoefA++; /* pATable[2 * i + 1] */ CoefA2 = *pCoefA; /* pSrc[2 * i] * pATable[2 * i] */ outR = *pSrc1 * CoefA1; /* pSrc[2 * i] * CoefA2 */ outI = *pSrc1++ * CoefA2; /* (pSrc[2 * i + 1] + pSrc[2 * fftLen - 2 * i + 1]) * CoefA2 */ outR -= (*pSrc1 + *pSrc2) * CoefA2; /* pSrc[2 * i + 1] * CoefA1 */ outI += *pSrc1++ * CoefA1; CoefB1 = *pCoefB; /* pSrc[2 * fftLen - 2 * i + 1] * CoefB1 */ outI -= *pSrc2-- * CoefB1; /* pSrc[2 * fftLen - 2 * i] * CoefA2 */ outI -= *pSrc2 * CoefA2; /* pSrc[2 * fftLen - 2 * i] * CoefB1 */ outR += *pSrc2-- * CoefB1; /* write output */ *pDst1++ = outR; *pDst1++ = outI; /* write complex conjugate output */ *pDst2-- = -outI; *pDst2-- = outR; /* update coefficient pointer */ pCoefB = pCoefB + (modifier * 2U); pCoefA = pCoefA + ((modifier * 2U) - 1U); i--; } pDst[2U * fftLen] = pSrc[0] - pSrc[1]; pDst[(2U * fftLen) + 1U] = 0.0f; pDst[0] = pSrc[0] + pSrc[1]; pDst[1] = 0.0f; } /** * @brief Core Real IFFT process * @param[in] *pSrc points to the input buffer. * @param[in] fftLen length of FFT. * @param[in] *pATable points to the twiddle Coef A buffer. * @param[in] *pBTable points to the twiddle Coef B buffer. * @param[out] *pDst points to the output buffer. * @param[in] modifier twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table. * @return none. */ void arm_split_rifft_f32( float32_t * pSrc, uint32_t fftLen, float32_t * pATable, float32_t * pBTable, float32_t * pDst, uint32_t modifier) { float32_t outR, outI; /* Temporary variables for output */ float32_t *pCoefA, *pCoefB; /* Temporary pointers for twiddle factors */ float32_t CoefA1, CoefA2, CoefB1; /* Temporary variables for twiddle coefficients */ float32_t *pSrc1 = &pSrc[0], *pSrc2 = &pSrc[(2U * fftLen) + 1U]; pCoefA = &pATable[0]; pCoefB = &pBTable[0]; while (fftLen > 0U) { /* outR = (pIn[2 * i] * pATable[2 * i] + pIn[2 * i + 1] * pATable[2 * i + 1] + pIn[2 * n - 2 * i] * pBTable[2 * i] - pIn[2 * n - 2 * i + 1] * pBTable[2 * i + 1]); outI = (pIn[2 * i + 1] * pATable[2 * i] - pIn[2 * i] * pATable[2 * i + 1] - pIn[2 * n - 2 * i] * pBTable[2 * i + 1] - pIn[2 * n - 2 * i + 1] * pBTable[2 * i]); */ CoefA1 = *pCoefA++; CoefA2 = *pCoefA; /* outR = (pSrc[2 * i] * CoefA1 */ outR = *pSrc1 * CoefA1; /* - pSrc[2 * i] * CoefA2 */ outI = -(*pSrc1++) * CoefA2; /* (pSrc[2 * i + 1] + pSrc[2 * fftLen - 2 * i + 1]) * CoefA2 */ outR += (*pSrc1 + *pSrc2) * CoefA2; /* pSrc[2 * i + 1] * CoefA1 */ outI += (*pSrc1++) * CoefA1; CoefB1 = *pCoefB; /* - pSrc[2 * fftLen - 2 * i + 1] * CoefB1 */ outI -= *pSrc2-- * CoefB1; /* pSrc[2 * fftLen - 2 * i] * CoefB1 */ outR += *pSrc2 * CoefB1; /* pSrc[2 * fftLen - 2 * i] * CoefA2 */ outI += *pSrc2-- * CoefA2; /* write output */ *pDst++ = outR; *pDst++ = outI; /* update coefficient pointer */ pCoefB = pCoefB + (modifier * 2U); pCoefA = pCoefA + ((modifier * 2U) - 1U); /* Decrement loop count */ fftLen--; } }